check_vpn: openvpn plugin will not check open port if on udp, checking correct port
check_vpn/openvpn: port check only if specified 'tcp' proto
typo in curl command
check_vpn: specific options for openvpn tcp connection
check_vpn: added comment about --nobind
Merge pull request #6 from danfruehauf/openvpn_port_proto

check_vpn: port check correct port, no port check if udp